Measuring gas pump

ABSTRACT

A measuring gas pump ( 1 ) including a pump housing ( 2 ) with a pump chamber ( 3 ) inside which is sealed by a working membrane ( 5 ). The membrane ( 5 ) is connected by a connecting rod ( 8 ) or a similar type of lifting device to a crank mechanism ( 9 ). A heating device is provided in the upper area of the pump housing, specifically in the pump head ( 10 ). On one hand, in the drive-transmission area between the head of the connecting rod ( 6 ) on the membrane side and the crank mechanism ( 9 ), there are holes ( 11 ) for the reduction of heat transfer to the crank mechanism which are spaced in a longitudinal direction of the connecting rod and which are also diametrically opposed, in peripheral direction, with a resulting reduction in heat conductivity. On the other hand, there is an enlargement of the surface area, at least in the area adjacent to the crank mechanism, for purposes of heat dissipation, specifically through cooling ribs ( 12 ).

BACKGROUND

[0001] The invention concerns a measuring gas pump with a pump housingcontaining a pump chamber sealed with a working membrane which isconnected to a crank mechanism through a connecting rod with a crankmechanism, and in which a heating device is provided in the upper areaof the pump housing, as well as with a heating device located in theupper area of the pump housing. In the drive-transmission area betweenthe head of the connecting rod on the membrane side and the crankmechanism, holes are provided for purposes of reducing heat transfer tothe crank mechanism by reducing heat conductivity. These holes arespaced in the longitudinal direction of the connecting rod and areoffset in peripheral direction.

[0002] In U.S. Pat. No. 4,790,730, a measuring gas pump of the typementioned above, for the delivery of hot measured gasses, is known, inwhich the working membrane sealing the pump chamber is connected to acrank mechanism by a connecting rod. In the pump previously known fromU.S. Pat. No. 4,790,730, a heating device is located in the upper areaof the pump housing. With the help of this heating device, the areaswhich come into contact with the gas to be measured are supposed to bemaintained at a pre-determined temperature equivalent to that of theextraction point of the gas to be measured, in order to prevent a dropin temperature of the gas to be measured in the area of the pump chamberand to avoid a condensation of gas components to be analyzed and afalsification of the measurement results.

[0003] In the pump of U.S. Pat. No. 4,790,730, holes, spaced in thelongitudinal direction of the connecting rod and offset in peripheraldirection, are provided for the purpose of reducing heat transfer to thecrank mechanism in the drive-transmission area between the head of theconnecting rod on the membrane side and the crank mechanism, thereforereducing heat conductivity. At the same time, however, the connectingrod in the area of these holes features a larger connecting rodcross-section, thus reducing the thermal resistance in an undesirablemanner.

SUMMARY

[0004] The object of this invention is to reduce the transfer of heatbetween the pump head and the crank mechanism, particularly to thebearing of the connecting rod, while largely avoiding the disadvantagesdescribed above.

[0005] In order to accomplish this task, it is suggested that anenlargement of the surface area be provided in the form of cooling ribs,for purposes of heat dissipation, located in the area of the head of theconnecting rod adjacent to the crank mechanism where the rod portion ofthe connecting rod is connected, and that at least one hole be providedfor reducing heat conductivity and/or for heat dissipation to theadjacently located cooling ribs in the area between the cooling ribs andthe bearing of the connecting rod.

[0006] The combination of these simple-to-institute measures leads to aneffective reduction of the temperature of the bearing of the connectionrod, resulting in a corresponding extension of service life. In the headof the connecting rod adjacent to the crank mechanism of the inventedgas pump, one or several holes are also provided in the area between thecooling ribs and the bearing of the connection rod for reducing heatconductivity and/or for dissipating heat to the adjacently locatedcooling ribs. On the one hand, this reduces the surface area of the heatconducting cross-section. On the other hand, air circulation and,therefore, heat dissipation can be achieved by means of these holes. Inaddition, this favors the drawing off of heat to the cooling ribs.

[0007] Cooling by means of the cooling ribs is especially effective bymeans of the crank or eccentric movement, so that practically noelevated temperature load on the bearing of the connection rod and itssurrounding area occurs, in spite of higher temperatures in the area ofthe head of the connecting rod.

[0008] The holes, spaced on the side and offset in peripheral direction,minimize the heat conducting cross-section of the connecting rod, butreduce the stability only insignificantly by the longitudinal offset ofthe holes. The heat still occurring at the end of the connecting rodadjacent to the crank mechanism can then be effectively dissipated intothe environment through the increase in surface area provided by thecooling ribs.

[0009] The adjacent holes should be diametrically opposed at 90° to eachother with a medium amount of distance that is no less than thediameter. Through this side offset of the holes in the longitudinaldirection of the connecting rod, the holes indeed interlock, the resultbeing an especially good aeration and cooling in this area as well, butthe stability of the connecting rod is preserved to the greatest extentpossible.

[0010] Another advantage is that the connecting rod is made of steel,specifically from stainless steel. Stainless steel has the advantageover the aluminum used most of the time for connecting rods, since ithas less heat conductivity but good stability characteristics at thesame time.

[0011] The measures in accordance with one or more of Claims 1 through 5are preferably installed in a measuring gas pump featuring heatinsulation that encompasses at least the pump head, so that the heatinsulation is primarily established through an isolation housing whoseinner wall is spaced from the pump head for the formation of a gasisolation layer. Through this effective insulation of the pump head,practically no heat can escape, so that it becomes particularlyimportant to institute the measures pertaining to this invention forreducing the transmission of heat in the direction of the bearing of theconnecting rod and crank mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention, along with its essential details, is described inmore detail below.

[0013] In the drawings:

[0014]FIG. 1 is a longitudinal section of a measuring gas pump,

[0015]FIG. 2 is a partial cutaway of a connecting rod, and

[0016]FIG. 3 is a cross-section of a connecting rod in the area of ahole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A measuring gas pump 1 shown in FIG. 1 includes a pump housing 2with a pump chamber 3 located inside which is sealed on one side by apump head cover 4 and on the other side by a working membrane 5 as wellas a head of the connecting rod 6. The working membrane 5 is on theoutside between the pump head cover 4 and a circular housing part 7 aswell as centrally placed on the head of the connecting rod 6 andconnected to a crank mechanism 9 through a connecting rod 8 connected tothe head of the connecting rod 6.

[0018] In this measuring gas pump, which is preferably a heated pump, aheating device is provided in the pump head 10. In this way, the pumphead can be heated to over 100° C. as needed. In order to prevent a heattransfer from the pump head 10 to the crank mechanism 9 occurring to adegree that is damaging to the bearing of the connecting rod, measuresfor reducing the transfer of heat to the crank mechanism 9 are providedin the area of the drive-transmission.

[0019] In order to reduce heat conductivity, holes 11 offset inperipheral direction are provided, spaced in the longitudinal directionof the connecting rod. As shown in the enlarged illustration in FIG. 2,it can be clearly seen that nearby holes 11 are placed at 90° to eachother, featuring a middle distance of less than the hole diameter. Thehole channels are connected to each other in this way. In this way, theheat conductivity of the connecting rod 8 is minimized on one hand,while the holes 11 provide favor good ventilation and therefore goodheat dissipation. Through the offset of the holes 11 and the connectionof their channels, good stability values are maintained in spite of thereduction of heat conductivity and the increased dissipation of heatachieved.

[0020] In the preferred embodiment, two adjacent holes 11 are provided.Depending on the length of the connecting rod, however, more than twoholes 11 can also be provided.

[0021] In order to dissipate heat, an enlargement of the surface area isprovided at least in the area around the crank mechanism by means ofcooling ribs 12. In the preferred embodiment, these are situated in theconical transfer area of the head of the connecting rod near the crankmechanism. This achieves an effective dissipation of heat in this area;this can be supported even more by preferably providing one or moreadditional holes 11 a between the cooling ribs 12 and the bearing of theconnecting rod. The holes 11 a are situated in such a way that heattransfer to the nearby cooling ribs and a resulting dissipation of heatin that area also takes place, as indicated by the arrow in FIG. 1.

[0022] The combination of reduced heat conductivity on the one hand andthe increased possibility of heat radiation on the other hand results ina large drop in temperature between the pump head 10 and crank mechanism9, so that only normal operating temperatures which are non-damaging forthe bearing of the connecting rod occur in the area of the pump head 10,in spite of higher operating temperatures.

[0023] The measures described above for reducing the heat transfer fromthe pump head to the crank mechanism, have an especially advantageouseffect in a gas measuring pump which includes heat insulationencompassing the pump head, formed primarily by an isolation housing 13whose inner wall is spaced from the pump head 10 in order to form a gasisolation layer 14 for the pump head 10.

1. Measuring gas pump (1) comprising a pump housing (2), with a pumpchamber (3) located therein that is sealed with a working membrane (5),that is drivingly connected by a connecting rod (8) to a crank mechanism(9), and include a heating device in an upper area of the pump housing(2), whereby in the drive transmission area between a membrane side of ahead (6) of the connecting rod and the crank mechanism (9) to reduce theheat transfer to the crank mechanism (9) by reducing heat conductivity,holes (11) are located in the connecting rod spaced in a longitudinaldirection and offset in a peripheral direction, characterized in that,for heat dissipation, cooling ribs (12) are provided for an enlargedsurface are in the connecting rod head (6) adjacent to the crankmechanism where a rod portion of the connecting rod is connected, andthat at lease one hole (11) for reducing the heat conductivity and/or todissipate heat to the adjacently located cooling ribs (12) is providedin an area between the cooling ribs (12) and the connecting rod bearing.2. Measuring gas pump according to claim 1, characterized in that thecooling ribs (12) are provided is a conical junction area of the rodportion of the connecting rod adjacent to the crank mechanism connectingrod head (6).
 3. Measuring gas pump according to claim 1, characterizedin that adjacent ones of the holes (11) are diametrically opposed toeach other at a 90° angle and have a middle distance from each other ofless than a diameter of the holes.
 4. Measuring gas pump according toclaim 1, characterized by the connecting rod (8) being formed of steel,specifically of stainless steel.
 5. Measuring gas pump according toclaim 1, further comprising a heat insulation encompassing at least thepump head, the heat insulation being principally formed by an isolationhousing (13) having an inner wall that projects from the pump head (10)to form a gas isolation layer.